Piezoelectric/electrostrictive devices of the above-described type have been actively developed as an actuator for precision machining; as an actuator for controlling the position of a read and/or write element (e.g., a magnetic head of a hard disk drive) for reading and/or writing optical information, magnetic information, or the like; as a sensor for converting mechanical vibration to an electrical signal; or as a similar device.
Japanese Patent Application Laid-Open (kokai) No. 2001-320103 discloses an example of such a piezoelectric/electrostrictive device, which is shown in FIG. 13. The piezoelectric/electrostrictive device includes a stationary portion 100; thin-plate portions 110 supported by the stationary portion 100; holding portions (movable portions) 120 provided at corresponding tip ends of the thin-plate portions 110 and adapted to hold an object (e.g., a magnetic head of a hard disk drive); and piezoelectric/electrostrictive elements 130 formed at least on corresponding surfaces of the thin-plate portions 110, each piezoelectric/electrostrictive element 130 including a plurality of electrodes and a plurality of piezoelectric/electrostrictive layers which are laminated alternately. In the piezoelectric/electrostrictive device, an electric field is generated between electrodes of the piezoelectric/electrostrictive elements 130 to thereby expand and contract the piezoelectric/electrostrictive layers of the piezoelectric/electrostrictive elements 130, whereby the thin-plate portions 110 are deformed. The deformation of the thin-plate portions 110 causes displacement of the holding portions 120 (accordingly, displacement of the object held by the holding portions 120).
The piezoelectric/electrostrictive device of FIG. 13 is manufactured as follows. Firstly, as shown in FIG. 14, a plurality of ceramic green sheets (and/or a ceramic green sheet laminate) are prepared. As shown in FIG. 15, these ceramic green sheets are laminated together and then fired, thereby forming a ceramic laminate 200. As shown in FIG. 16, piezoelectric/electrostrictive laminates 210, each including a plurality of electrodes and a plurality of piezoelectric/electrostrictive layers which are laminated alternately, are formed on the surface of the ceramic laminate 200. Through wire sawing (or, for example, dicing) by use of a wire saw WS, the piezoelectric/electrostrictive laminates 210 are cut along cutting lines C1 to C4 shown in FIG. 17, thereby yielding the piezoelectric/electrostrictive device.
Meanwhile, in the case where the above-disclosed piezoelectric/electrostrictive device is actually used (for example, in the case where the device is used as an actuator for the positioning of the magnetic head of a hard disk drive), moisture may sometimes deposit on lateral end surfaces (cut planes along the cutting line C3 or C4 in FIG. 17) of piezoelectric/electrostrictive elements 130. Such moisture can be caused by, for example, condensation or the like of water vapor in an atmosphere (in the air).
When moisture deposits on lateral end surfaces of piezoelectric/electrostrictive elements 130 (particularly on lateral end surfaces of piezoelectric/electrostrictive layers as parts of lateral end surfaces of piezoelectric/electrostrictive elements 130), the electric resistance of the piezoelectric/electrostrictive layers on the lateral end surfaces of which moisture has deposited lowers and thereby electric leakage tends to occur between the electrodes on both the sides that interpose the respective piezoelectric/electrostrictive layers. Otherwise, so-called ion migration is promoted on the lateral end surfaces of the piezoelectric/electrostrictive layers due to the existence of the moisture that deposits on the lateral end surfaces and, as a result, short circuit tends to occur between the electrodes on both the sides that interpose the respective piezoelectric/electrostrictive layers on the lateral end surfaces of which the moisture has deposited.
When such electric leakage occurs, voltage between the electrodes lowers and thereby the strength of the electric field formed between the electrodes weakens. As a result, the amount of the expansion and contraction of the piezoelectric/electrostrictive layers reduces and the piezoelectric/electrostrictive elements 130 (namely the piezoelectric/electrostrictive device) cannot attain intended operations. Further, when such short circuit occurs, voltage is not generated between the electrodes, thereby the piezoelectric/electrostrictive elements 130 do not expand or contract, and as a result the piezoelectric/electrostrictive elements 130 (namely the piezoelectric/electrostrictive device) cannot operate.
In addition, when such an above-disclosed piezoelectric/electrostrictive device is used as, for example, an actuator for the positioning of the magnetic head of a hard disk drive, the attachment of debris, dust, or the like on a hard disk, etc., may cause incorrect reading/writing of information. Hence, the piezoelectric/electrostrictive device is to be placed in an environment where the generation of debris, dust, or the like (the generation of debris, dust, or the like may hereunder be referred to as “dust generation” occasionally) can be suppressed to a lowest possible level.
In such a case, the above-disclosed piezoelectric/electrostrictive device is used in the state where the lateral end surfaces (cut planes along the cutting line C3 or C4 in FIG. 17), constituting a single planar plane, of the device face the surface of the hard disk with a relatively small gap in between and hence it is particularly necessary to prevent dust generation caused by the separation of microparticles (the separation of microparticles may hereunder be referred to as “particle separation” occasionally) from the lateral end surfaces (cut planes along the cutting line C3 or C4 in FIG. 17) of the constituent elements constituting the lateral end surfaces of the piezoelectric/electrostrictive device. From the above viewpoint, test items related to dust generation have been added to such a piezoelectric/electrostrictive device in recent years.
In view of the above situation, the above-disclosed piezoelectric/electrostrictive device is required to effectively suppress the deposition of moisture on the lateral end surfaces of piezoelectric/electrostrictive elements 130 and dust generation from the lateral end surfaces when the piezoelectric/electrostrictive device is actually used.